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Can I Increase the Read Range of Passive UHF RFID Tags?
Is this possible—and, if so, how would it be done?
There are a few things you could try, depending on the tag design, the operating environment and the material of the item being tagged. First, you could increase the gain of the reader antenna, if it is legally permissible to do so in your country. The gain is essentially the amount of energy being emitted by the reader antenna. If the antenna emits a more powerful signal, then the tag can receive enough energy to respond, even if it is further away. But governments control power output to prevent people from cranking up radio devices and interfering with other devices using the same portion of the radio spectrum.
If it is a dipole tag, you could use a linear-polarized reader antenna, rather than a circular-polarized antenna. Linear-polarized antennas focus reader energy in a narrow beam, rather than meeting energy in a cone shape, to energize the tag regardless of orientation. A linear-polarized antenna can be set up either vertically or horizontally. You would need to be sure the beam's orientation matched that of the tag. If the tag is vertical and the reader antenna is horizontal, you won't be able to read the tag.
You should check if multipathing is reducing the read range. This occurs when waves reflecting off the floor, ceiling or nearby metal objects counteract the reader's signals, essentially canceling them out like noise-cancellation headphones. And you should also make sure you are utilizing tags designed for the specific material you are tagging. If you are trying to read a tag on a metal object but the tag is not designed to work near metal, then the metal object will detune the tag, greatly reducing the read range. Different materials, including glass, have different dielectric constants, which means they conduct electricity and can detune the tag—but you can compensate for this by employing a tag designed to work on glass, metal or other materials.
—Mark Roberti, Founder and Editor, RFID Journal
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